Fiber optic cables include optical waveguides such as optical fibers that transmit optical signals, for example, voice, video, and/or data information. One type of fiber optic cable configuration includes optical waveguides disposed within a tube, thereby forming a tube assembly. Generally speaking, the tube protects the optical waveguides; however, the tube assembly must also meet other performance requirements. Consequently, conventional tube assemblies filled the tube with a thixotropic grease for meeting the necessary performance requirements.
Specifically, the thixotropic grease allowed the optical waveguides to have some relative movement between the optical waveguides and the tube to accommodate bending. Additionally, the thixotropic grease adequately couples the optical waveguides with the tube, thereby inhibiting the optical waveguides from being displaced within the tube when, for example, pulling forces are applied to install the cable. The thixotropic grease also inhibited the migration of water therein. Furthermore, the type of thixotropic grease was carefully selected since the tube assembly generally required operation over a range of temperatures without undue optical performance degradation due to viscosity changes in the thixotropic grease.
Although, the thixotropic grease worked well it had several drawbacks. First, the thixotropic grease was messy and required cleaning from the optical fiber before connectorization. Removing the thixotropic grease was time consuming and requires the craftsman to carry the necessary cleaning materials and supplies. Additionally, the thixotropic grease changes viscosity with temperature and with elevated temperatures it may flow out of the end of the cable. Several cable designs have attempted to remove the thixotropic grease, but with limited success since the thixotropic grease served several distinct functions.